mod front_of_house {
    pub mod hosting {   // 使用pub关键字暴露路径
        pub fn add_to_waitlist() {} // 如果要调用这个函数，这里也要用pub关键字

        fn seat_at_table() {}
    }

    mod serving {
        fn take_order() {}

        fn server_order() {}

        fn take_payment() {}
    }
}

pub fn eat_at_restaurant() {
    // 绝对路径
    crate::front_of_house::hosting::add_to_waitlist();

    // 相对路径
    front_of_house::hosting::add_to_waitlist();
}
